Automatic,burst firing,gun



United States Patent Inventors Robert E. Chiabrandy;

. George H. Bloom, Burlington, Vermont Appl. No. 787,069 Filed Dec. 26,1968 Patented Oct. 27, 1970 Assignee General Electric Company acorporation of New York AUTOMATIC, BURST FIRING, GUN

Bomheim et a1 2,962,935 12/1960 Hepperle 89/157UX PrimaryE.raminerBenjamin A. Borchelt Assistant Examiner-Stephen C. BentleyAttorneys-Bailin L. Kuch, lrving M. Freedman. Harry C.

Burgess, Frank L. Neuhauser and Oscar B. Waddell ABSTRACT: An automatic,burst firing howitzer is provided having a single tube or gun barrel,and two alternatively and sequentially utilized firing chambers whichreciprocate with the tube in recoil and counterrecoil. A loading systemis provided to load cartridges sequentially into the respective firingchamber approximately at the nadir of its recoil travel, which travelmay vary in extent in response to the particular elevation of the tubeand the powder charge fired. The loading system includes a hydrauliccylinder and spring system for continuously monitoring the recoilvelocity of the chambers and for traversing the cartridge in theappropriate direction and with the appropriate velocity to fully chamberthe cartridge at or near said nadir.

' Pitnted 0. 27, 1910 3,535,980

INVENTORS;

ROBERT E. CHIABRANDY, GEORGE H. aLoogn,

/ THEIR ATTORNEY.

Patented Oct. 27,1970

Sheet INVENTORSI ROBERT E. CHIABRANDY,

I GEORGE H. BLOOM,

I/ITHEIR ATTORNEY.

Patented Qct.27, 1970 3.535.980

lNVENTORS- ROBERT E. CHIABRANDY. GEORGE H. BLOOM;

BY I

/ mam ATTORNEY.

Patented Oct. 27, 1970 3,535,930

Sheet "3' of 5 INVENTORs: ROBERT E. CHIABRANDY,

luv llt llllllllllll mm m 8 S 4. N 4 NM Mm GEORGE H. BLOOM,

THEIR ATTORNEY.

v llllll l 1 o- Fm Q0 E N9 on I AUTOMATIC, BURST FIRING, GUN

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to rapid firing artillery; and especially to an artillery pieceadapted to fire 'a rapid burst of rounds, e.g., a burst firing howitzer.

2. Prior Art The conventional heavy artillery piece includes a barrelassembly and a breech mechanism mounted on a recoil support mechanism.The distance of the recoil travel is mainly a function of the recoilimpulse generated by the charge of powder fired to project theprojectile from the weapon. It is also, inter alia, a function of theangle of elevation of the barrel assembly. Conventional weapons designedfor relatively rapid fire usually fire fixed ammunition, i.e., theprojectile is fixed to its powder canister. Thus, for a given type ofammunition, the powder charge fired will be substantially uniform, andthe recoil impulse will be substantially uniform. The minor variationwhich might be caused by changes in the angle of elevation can becompensated for by changing the stiffness of the recoil buffer system.Thus, in fixed ammunition firing weapons, the distance of recoil travelis substantially invariable, i.e., subject to a variation of less than10 percent. Historically, a round of ammunition was loaded into thebreech after the breech mechanism had completed its counterrecoil traveland was in battery, i.e., in its firing, forwardmost position. Thisrequires a firing cycle wherein the time spent in recoil andcounterrecoil is wasted as far as loading is concerned. In an cffort toshorten the firing cycle, some automatically loaded weapons haveprovided for an initiation of the loading operation while the weapon istraveling in counterrecoil. However, these weapons have required aninvariable distance of travel, i.e., the point at which the magazineshifted the round to the breech loading device was fixed. Such a systemworks quite well for relatively lightweight weapons, such as the 75mm AAgun and lighter weapons. which fire fixed ammunition.

However. in a weapon which fires semifixed ammunition the distance oftravel is not invariable. Semifixed ammunition permits the canoneer towithdraw the projectile from the powder canister and to change thequantity of powder contained therein. The variable quantity of powderfired will provide a variable recoil impulse.

In a 105mm howitzer firing semifixed ammunition, a variation of recoilimpulse of :1 may be encountered. With an ideal spring recoil system, avariation of recoil travel of 25:1 would result. However, by use ofpreloaded spring-hydraulic bufiers, this can be reduced to a 4:1variation of recoil travel, e.g., 72 to 17 inches. A skilled gun crewcan start loading about the time the weapon commences counterrecoil.that is before it reaches battery. However, conventional loading devicescould not, since they would not have an invariable point at which toshift from the magazine to the breech loading mechanism.

A related problem is that the fuzes and rotating bands on manyprojectiles are quite sensitive to acceleration. It is desirable tochamber the roundat as low a relative velocity between the round and thebreech as possible. For this reason also, it is desirable to chamber theround at or about the nadir or the point of maximum recoil travel. atwhich point the velocity of the breech will be zero.

SUMMARY OF THE INVENTION It is an object of this invention to provide anammunition loading system for automatically, rapidly loading arelatively heavy artillery piece with semifixed ammunition; whichammunition may be acceleration-sensitive with respect to its fuze androtating band.

Consequently, it is an object of this invention to provide an ammunitionloading system which is especially adapted to automatically chamber eachround at substantially the nadir of the recoil travel, wherever, andwhenever such nadir occurs.

A feature of this invention is the provision of an ammunition loadingsystem which continually monitors the recoil velocity ofgthe breech andcontinually traverses the round to be chambered in the appropriatedirection and at an appropriate velocity with respect to the breech sothat the round will be chambered at the nadir of the recoil travel.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features andadvantages of the invention will be apparent from the followingspecification thereof taken in conjunction with the accompanying drawinginlwhich:

FIG. 1 is a view in perspective of a representative howitzer embodyingthis invention;

FIG. 2 is a side in elevation of the tipping parts of the howitzer ofFIG. 1;"

FIG. 3 is a top plan view of the tipping parts of FIG. 2;

FIG. 4 is a rear view in elevation of the tipping parts of FIG.

FIG. 5 is a front view in elevation of the tipping parts of FIG. 2;

FIG. 6 is a side view in elevation, in partial cross section, of thehydrospring chambering mechanism;

FIG. 7 is a rear view, in cross section of FIG. 6, taken along the plane7-7;

FIG. 8 is a detail side view in elevation of chamber indexing mechanism;and

FIGS. 9 and 10 are velocity-displacement diagrams illustrating loadingunder high and low recoil conditions. respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT A rapid-fire howitzer embodyingthis invention is illustrated in the drawing. When compared toconventional mm howitzers. the open trails of this weapon are longer.the azimuth axis is forward of the elevation trunnions, and a rotarymagazine is affixed to the cradle assembly and placed above the breech.The weapon has a two-chambered indexing breech and a variabledisplacement ramming stroke.

The two-chambered breech, which is fixed fore and aft to a breechsupport, recoils with the firing barrel. which is located axially aheadof the lower chamber. These parts recoil and counterrecoil on the cradleways. A rammer and tray assembly, which is not rigidly attached to therecoiling parts, travel on a center rod. A top carriage supports thetipping parts at the elevation trunnion and by means of elevating ballscrews. The top carriage is rotatably supported by the bottom carriage,to which are attached a firing pedestal, firing trails, and the torsionbar wheel suspension.

The weapon has four major components: the recoiling parts. the cradleassembly, the top carriage, and the bottom carriage.

A. Recoiling Pans Asembly The recoiling parts assembly consists of abreech 12, a tube 14, a breech support assembly 16, an extractorassembly 20, a main cam 22 having two diametrically spaced apartcycloidal cam slots 23, intersected fore and aft by two diametricallyspaced apart longitudinal return slots 230, a recoil brake 24 and arecuperator 26.

The breech I2 is a member with a generally elliptical cross section. Ithas two chambers 28, 29 whose internal dimensions and rifling aresimilar to the same length of conventional tube. This breech 12 rotateson the cam 22, which in turn is supported by, and keyed to, a center rod32. Both the breech and the cam are free to slide on the center rodduring recoil. Two cam followers 34, 36, diametrically opposite, arefastened to the inside of the breech to engage the cam slot 23.

Prime structural support for the breech comes from the fore and aftsections of the breech support structure 16. On the front end of thebreech around both chambers, are the gas seals 38, 40 which are of thering seal type. Adjacent each bore on the front end of the breech is arespective finely machined tapered centered hole 42 (one not shown) anda pin 45 to assure tube-to-breech alignment while firing.

lower chamber of the breech assembly, which is the firing chamber, andis supported circumferentially by a section at the front of the breechsupport assembly 16. The tube is attached to the breech structure byuninterrupted threads and locked to prevent rotation by the use of alocking key.

The rectangular breech support assembly 16 supports the breech 12 on thesliding bearing surfaces at both the front and rear. The sides of thisassembly provide the runners 48 that ride in the cradle ways 52, duringrecoil and counterrecoil. The aft end of this rectangular structuredevelops into the breech plate assembly 54. The breech plate 54 isplaced immediately to the rear of the breech. Its section issufiiciently great to withstand the loads created by the firingimpulses. This plate also keeps the round chambered when the weapon isin counterrecoil. Axially behind the lower chamber of the breech andhinged and locked to the breech plate is the horizontal-swingbreechblock 56, which has an interrupted thread. (This breechblock isonly used when a misfire is to be removed.)

The extractor assembly 20 consists of two, individually hinged U-shapedhinged plates 60. Each fits into a respective recessed cutout 64 on therear face of the breech. Each plate has a set of arms which straddle therespective chambered round and bear against 180 degrees of the extractorplate rim of the round to insure a good bearing area during extraction.

The two main cam slots 23 are cut into the periphery of the main cam 22which is a tubular member. The inside diameter of the cam tube houses aratchet ann 68 that engages teeth 70 on the center rod 32 only duringcounterreeoil (skipping over the teeth during recoil). The cam slotconfiguration is that of a modifiied cycloid (with respect to time, notdisplacement). This cam slot is designed to produce minimum roller loadsat high zones of fire by reducing the angular and linear accelerationsof the breech and recoiling parts respectively.

Two hydrospring counterrecoil buffers mount on the forward end of thebreech support assembly. They are symmetrically placed about the firingtube, and act against the cradle assembly. The recoil brake 24 is alsomounted on the breech support assembly [6 and is located below the tube14. Two hydraulic lines connect it to the recuperator 26. Therecuperator has a free floating piston which provides recoil throttlingaction, and is nitrogen charged. Both of these hydraulic members havebeen made part of the recoiling parts to lower their center of mass andincrease their weight. The barrel centerline is coincident with thecenter of mass of the recoiling parts.

The round 30 is on a loading tray 102. with the base. or rear portion.of the round held against a ram 74 spaced aft of the recoiling breech12. In the event of low zone firing in a representative howitzer. thebreech moves back approximately l8 inches. The round. positioned inchesto the rear of the breech, must therefore. move forward to be chambered.A hydraulic cylinder [06, positioned at the center of the breech isacted upon by the force created by the hydraulic fluid, acting on thepiston 108 and passing through an orifice therein H0. in low zone (i.e..low recoil velocity pressure differential across the piston is low.Thus, the force against the piston is low. A gear rack 112 is formed asan extension of the cylinder, and recoils therewith. in moving rearward,it is engaged with and rotates a gear set 114 mounted in a housing 118which is loaded by a spring I16, and which housing is formed as anextension of the piston 108. The ram 74 has a rack 120 which is engagedby the gear set 114, so that the ram moves forward a related distance.The ratio of recoil travel to ram travel is set by the gear ratio. Thechambering of the round is determined by the balance between thehydraulic parameters, particularly the orifice coefficient the spring116, and the gear ratio discussed above.

As eounterrecoil begins, the reverse occurs. The breech 12 carries therack 112 forward causing the ram 74 and tray 102 to move aft. As thebreech retums to battery, the ram returns to its neutral position. Thegear housing is returned to its neutral position by action of thepreloaded spring 1 16.

In the event of high zone firing, the breech moves back at highervelocity. The hydraulic fluid in the cylinder creates pressure againstthe forward face of the piston, forcing it to accelerate aft. Thismotion is transmitted directly to the housing 118 in which the gear set1 14 is carried through the piston rod 122. This rearward motion, withrespect to the cradle, forcing the gear set to translate aft against thepreloaded spring 116. The gear rack, which is connected to the hydrauliccylinder, also moves aft at the speed of the recoiling parts. This rackmotion tends to rotate the gear set so as to produce forward motion ofthe ram 74. The net result of both the translation and rotation of thegear set is such that the ram moves aft and carries the tray aft with itby abutting an afi-projection on the tray. While moving rearward, theround 30 on the tray 102 is overtaken by the recoiling parts and ischambered at a relatively low velocity (the vector addition of the twovelocities). As the recoiling parts begin counterrecoil. with the roundin the chamber, the action of the preloaded spring 106 and the motion ofthe rack [12 result in the ram 74 moving forward to its neutralposition. The gear housing 118 is stopped at its neutral position by astop 124 which is fixed to the nonmoving center rod 32. The tray 102 isso constructed so that the ram 74 may move through it while ramming andalso receive adequate lateral stability from the tray which is supportedby two sway braces 126 which ride in slots 128 on the center rod 32. Anogive guide (not shown) is pivotally mounted to the tray. The ogiveguide forces the projectile to move afi with the case and thus precludesthe separation of the projectile from the case in semifixed ammunition.

B. Cradle Asembly The cradle assembly supports the recoiling partsassembly. This asembly consists of a cradle structure 202. a center rod32, a recoil brake piston rod (not shown). a center pin 45. a magazinefeeding mechanism 210. elevating trunnions 212 and fire controlequipment 214.

The cradle 202 is a rectangular structure with ribbed sections acrossthe bottom for increased strength and rigidity. The sides of the cradlehave steel inserts which serve as ways 52 for the recoiling parts. Theways are centered on the gun tube axis and extend for nearly the totallength of the cradle. The center rod 32, which fits through the centerof the breech, is rigidly mounted both front and rear to the cradleassembly. Sections of this rod have keyways and teeth 70 to assist inthe operation of the main cam 22 and the rammer tray mechanism 74. Thekeyway in the center rod 32 provides the cam 22 with a nonrotatingground" and stopping point as the cam-tube pawl 68 locks onto the teeth70 cut into the center rod 32. The rammer and tray are also keyed to thecenter rod.

A single-shot indexing mechanism is also located at the front end of thecradle structure. For ease of operation, the handle 226 itself islocated on the right side of the weapon to the rear of the breech. Thismechanism is linked through a cam and gear assembly 227 for the rotationof a circular cam 236. for indexing a feeder pawl 238. The cam 236 iscoupled to the feed shaft 239 which is located above the breech, and iscoupled to the magazine indexing mechanism 210.

The magazine indexing mechanism 210. which is mounted directly on thefront end of the magazine 240, contains two mechanisms and a standardset of bevel gears. One of the mechanisms is a torsional spring andratchet to permit rotation of the magazine during a longer time intervalthan allowed from direct rotation by the breech during recoil. Thesecond mechanism employs a slip clutch in the bevel gear set. In thismanner a pin can be placed in position to limit the number of rounds tobe fired. When the desired number of rounds has been fired, the pinbecomes locked and the magazine ceases to rotate.

Ammunition for burst fire is contained in the magazine 240. The magazineis supported by four connecting ribs 254 to the cradle. The magazinecontains three six-tooth sprockets 256, placed to give the roundssupport and guidance. The magazine can be loaded from up to five roundsthrough a doorway 258 in the rear. The doorway is shaped to prevent thesixth space from being loaded since this space is required for thefeeder pawl 238. A round-indexing link 260 is mounted on the feed shaft239 forward of the magazine 240 and above the breech. and is provided tocoordinate the motion of the magazine and the feeder pawl. The rotaryearn 236 supported by the feeder shaft 239 engages a follower 266 on thebreech to coordinate round feeding to the weapon cycle.

The elevating trunnions 212 are placed sufficiently rearward so that norecoil pit is required under any firing condition. The fire controlequipment 214 mounted on these trunnions consists of a direct-firetelescope mounted on the right side and an indirect-fire telescopemounted on the left.

C. Top Carriage and Equilibrators The top carriage assembly is astructure that provides sup port for the tipping parts and contains thetop carriage structure 370, elevating and traversing mechanism 372 andthe equilibrators 374.

The top carriage structure 370 contains the upper support 376 for themain an'muth bearing 378. From this bearing two sides frames reach up toelevation trunnions. providing support for the tipping parts. Theelevating mechanism is attached to each side of the top carriage andforward of the magazine. Two ball nuts are attached to both sides of thecradle while the ball screws and universal couplings are fixed to. andride with. the top carriage. Pitch and gear reduction of the ball screware provided to yield a convenient elevating rate per turn of thehandwheel.

An elevation handwheel is mounted on the right side of the carriage andis convenient for use with fire control apparatus. The handloadsrequired to elevate the weapon require a low maximum torque with fiverounds in the magazine. The ball screw and nut combination in thismechanism serves as a locking device, a mechanical force amplifier, anda means of rigidizing the top carriage structure. The traversingmechanism employs a partial gear, cut for 40 on the bottom carriagearound the main bearing, a worm wheel and a universal coupling. Thehandwheel on the left hand side of the weapon is also convenient for usewith fire control equipment. Gear staging in the traversing mechanismyields a convenient traversing rate per turn of the handwheel. lockingin this mechanism is provided by the use of a worm wheel and gear.

Equilibrators 374 are mounted between the top carriage and the cradle.They are coil-spring-loaded, of the pull type. These two equilibratorsmount symmetrically from both sides of the top carriage. back to thesides of the cradle.

D. Bottom Carriage The bottom carriage consists of the bottom carriagestructure 402. split trails 404. and spades 406. wheels 408, suspensionand jacking assembly 410.

The bottom carriage provides a seat for the main azimuth bearing andconnecting support for both the trails and wheel suspension. On thefront of this structure is a ribbed pedestal 412 on which the front endof the weapon rests when in the firing position. This pedestal has aspherical seat to allow easier placement of the weapon in extendedtraverse. Similarly. the carriage structure also provides a pin jointconnection for each of the trails. These open trails are of the box typeconstruction. They are tapered in height, width, and material thicknesswith internal ribs for additional strength. The s ades have a largeeffective ground bearing area.

The wheels and the suspension and jacking assembly are supported fromthe front end of the bottom carriage. The wheel assembly is supported ontwo pivoting links, which also incorporate shock absorbers for improvedroadability. Suspension is provided by two torsion bars, each onespanning the distance between the wheels. Lifting of the wheels toemplace the weapon on the pedestal is done by a ball screw andnut-coupled to a handcrank. The wheels can be raised off the ground toact as outriggers when the pedestal is lowered, which will prevent theweapon from overturning when the trails are lifted. This action liftsthe wheels and suspension links by unwinding the suspension torsionbars, thus lowering the weapon onto the pedestal. For traveling, thewheels are lowered to provide ground clearance for road travel.

WEAPON FUNCTION To understand the operation of the weapon, it isimportant to know the cycle of events in the burst fire sequence. Sinceall of the mechanized events must occur within the time of the naturalcycle," recoil and counterrecoil. the mechanical cycle is predicated onmaximizing the time available for automatic firing function the naturalcycle) and minimizing weapon complexity.

Determination of the automatic weapon sequence defines in large measurethe single-shot procedure. as well as the basic weapon design itself.

A. Cycle Burst Fire Procedure 1. Five rounds (or less) are loaded in themagazine.

2. One round is placed in the exposed chamber, and the breech is rotatedinto firing position, also bringing one round from the now-loadedmagazine to a position directly behind the top chamber.

3. The lanyard is pulled, the first round is fired. and recoil begins.

4. During recoil. the round that was placed behind the top breech isrammed into the breech.

5. Recoil ends between 20 and 68 inches from battery and. as the weaponbegins counterrecoil. the breech engages a fixed cam and beginsrotation.

6. As the breech rotates past the breech block. the fired case isextracted and ejected.

7. The breech continues rotation, indexing 180 in 19 inches, andcontinues forward. As it approaches battery position, a new round is fedbehind the top breech. The centering pin aligns the tube with the loaded(bottom) breech.

8. The round in the bottom chamber is fired and the cycle begins anew.

This operation can be represented schematically. indicating the timeduration for each phase of the cycle. Two conditions, Zones 2 and 7, arerepresented as shown in FIGS. 10 and 9, respectively.

This cycle is similar for the single shot firing sequence except thatthe breech must be indexed to a secondary position for hand loading.Once this operation is performed the cycle is similar to that for burstfire.

The weapon function will be analyzed by the various elements that makeup a cycle, i.e.. feeding, ramming, ejection.

B. Loading and Feeding The magazine. although it has six-toothsprockets. can accept only five rounds or less. The hinged door at therear of the magazine is shaped to expose only five spaces; the one spacerequired for the feeder pawl remains empty. As the rounds are placed intheir sprocketed positions. they become locked in axial position. Thisserves two purposes: first. should the weapon be elevated during theloading process, rounds will not fall backward out of the sprockets;and. second. the rounds need to be positioned accurately in the axialdirection to insure proper feeding onto the tray and rammer. Since theenergy for cycle operation is derived from recoil. one round must beinitially placed in the firing chamber. This is accomplished by turningthe indexing lever, which. through a gear train and linkage. causes thetapered centering pin to be withdrawn (approximately I inch) from thebreech, and the breech to then be rotated in a clockwise direction(looking forward) The same indexing lever motion drives the feeder shaft8 inches forward. This, through a cam and linkage, causes two actions tooccur simultaneously: first, the feeder pawl moves through an arc of 60from a position behind the breech into the space in the magazineallocated for it; second. the magazine sprockets index 60, placing around in the feeder pawl. This feeder pawl has a spring-loaded fingerthat enables it to grasp the round circumferentially for 225. In thismanner the round is secured during the feeding operation.

A round may now be loaded into the exposed chamber, and the indexinglever counterrotated. The same mechanisms as before cause the breech torotate into firing position. lock the centering pin and cause the feederpawl. now carrying a round, to rotate behind the top (empty) chamber.The magazine does not rotate at this time. The loading and feedingoperations have now been completed. The firing mechanism, once thecentering pin is in position. can be triggered by pulling the lanyard.

During the burst-firing sequence, these operations are carried outautomatically. Initiation of this action is triggered by the camfollower (affixed to the forward side of the breech at its greatestdiameter) and the feeder cam mounted on the feeder shaft. During thefirst 8 inches of recoil, the cam is actuated and rotation energy isstored in a spring in the magazine indexing mechanism. This energy canbe then employed to index the magazine (and rounds contained therein) 60over a longer period of time. Indeed, during the lowest cycle time,angular acceleration of the rounds can be held to 6 rad/sec. During thefeed cycle, where the round is carried from the magazine to the tray theresultant maximum acceleration (again for zone 7, the worst case) can beshown to be less than rad/see.

C. Centering The centering device insures that the firing breech andtube are in line within 0.015 inch. The rifling in the tube can beundercut to minimize the effect of possible slight misalignment.

As the recoiling parts approach battery position, angular position ismaintained indirectly through the center rod. One inch before batteryposition. a tapered pin on the cradle crigages a hole in the forward endof the breech. This action produces the necessary final alignment. Whenthe breech is to rotate manually for single-shot firing, the pin isautomatically withdrawn.

D. Ramming The function of the ramming mechanism is to chamber therounds fed onto the tray by the feeding pawl. This section, by thedesign of the cycle, must be accomplished during recoil. Two importantconsiderations will be stated prior to relating the functionaloperation. First, the length of recoil varies, depending on the zonefired and elevation angle, from a minimum of 20 inches to a maximum of68 inches. Second, fuze sensitivity limits chambering velocity to amaximum of 20 feet per second. The rammer itself is dovetailed to thecenter rod and attached through a spring and hydraulic damper to thebreech.

The required motion of the rammer (and tray) for all zones is obtainedthrough the operation of a hydraulic damper and a constant force negatorspring. The input signal to this system is the velocity and displacementof the recoiling parts. When the weapon is firing zone 2 at 5 elevation,recoil is 20 inches; thus the rammer must carry the case forward 20inches (the rear of the magazine is located 40 inches from the rear faceof the breech) to chamber the round. During this low velocity (maximumvelocity is 55.9 f.p.s. and the force created by the action of thehydraulic damper overcomes the spring force and the rammer and roundretreat back from the recoiling breech. The equation of operation is:

m=mass of tray, rammer and round, 2 slugs.

p=spring preload, 250 lb.

c=damping coeflicient, 0.55 lb.-sec.*/ft.

=angle of elevation, degrees.

k=spring gradient, 0.001 lb./ft.

g= gravitational constant, 32.2 fin/sec.

w 23,, :i.,= displacement, velocity and acceleration of the cartridge;ft., f.p.s., ftJsec.

a aE displacement, velocity of the recoiling mass, ft., f.p.s.

Intermediate zones of fire will result in recoiling velocities betweenthese two extremes. In the zone 2 case, the relative chambering velocityis 15.04 f.p.s. For zone 7, the relative chambering velocity is 7.5f.p.s. The round, during this sequence, is being accelerated rearward atl5l ftJsecF. The projectile is held by the yoke that grips the rotatingband. This continues until the breech begins to overtake the rear of theprojectile. In so doing it drives the spring-loaded yoke away from therotating bands. The round. if the rammer stopped completely at thispoint, would have a chambering velocity of approximately 26 f.p.s. Themechanism can be made to produce constant velocity of the rammer fromthe time that the breech causes disengagement of the yoke and round. Inthis instance, the round continues rearward at 15.0 f.p.s. The round ischambered at 58.5 inches back of the battery position. At this time, therelative chambering velocity is only 7.5 f.p.s. Since there is noacceleration during this period, there is no possibility ofcase-projectile separation.

During this sequence the tray will move with the rammer. When the trayis below the magazine waiting to receive a round in the fully extendedcondition, its length is 26 inches. As the breech and rammer cometogether. and the nose of the projectile enters the breech, the traybegins to telescope. The tray is shaped to allow the round to beadvanced over it and be chambered without shearing the rotating bands.When the round is fully chambered, the rammer and tray have an effectivelength of 15 inches. This eliminates the need for a recoil pit whenfiring at high zone and high elevations.

E. Breech Operation During recoil the breech translates rearward.engaging the main cam tube after 20 inches of recoil and thereaftercarrying the cam tube with it. The breech does not rotate since. througha secondary straight line cam path. it is keyed to the center rod. Thecam tube has a dog latch that skips over the teeth on the center rod.These teeth exist from 20 to 68 inches behind battery. When the weaponceases recoiling (at a point between 20 and 68 inches. determined byweapon elevation and zone) and begins counterrecoil. the dog engages thetooth in that location on the center rod. This action locks the cam tothe stationary center rod in both translation and rotation. and preventsit from moving forward with the recoiling mass. Two cam followers L5 in.diameter each). located diametrically apart on the breech innerdiameter, are engaged by the cam and forced to rotate. thus rotating thecomplete breech assembly. The cam is a modified cycloid designed toimpart 180 of rotation to the breech in the first 19 inches of recoil.(Since the minimum recoil distance is 20 inches, this leaves l inch forengaging the centering pin.) The cam design is such that only l ofrotation occurs during the last 3 inches (from inch 15- l9) of travel.This allows time for damping the angular oscillation of the assembly.The cam has been designed to minimize the rotational and translationalaccelerations and thus keep the resultant forces down. Thus the highestangular acceleration occurs when the breech is just beginning tocounterrecoil and the translational acceleration is low. The cam insuresthat, under what is potentially the most severe condition, zone 7, theresultant angular displacement plotted against time is a cycloid. Duringthis rotational cycle, ejection takes place. As the breech comes to theend of the first 20 inches of counter recoil, the cam followers engage alatch on the dogs. lifting them out of the center rod teeth. The camtube is then 0 carried back with the breech. A spring drives the camtube back to the position it held at the initiationof the cycle.

F. Extraction and Ejection Extraction of the fired case is begun duringcounterrecoil when the breech has rotated 68. bringing it clear of thebreechblock. At this point (the time of this occurrence changes with thezone) the ejector plate with its U-shaped fingers in front of the (justfired) case rim is struck by a finger on the cam tube, which has noforward velocity at this point. v

The extractor plate is constrained to pivot about one end and drive thecase out of the breech, when struck by a protrusion on the cam wall. Thegeometry of the ejector is such that the velocity imparted to the caseis three times the counterrecoil velocity at that time, and directedrearward.

' The minimum ejection velocity occurs at zone 2 and is 18.0

f.p.s.; the maximum is 42 f.p.s. at zone 7. The rotation of the breechduring this time gives each ejected case a tangential velocity.perpendicular to the rearward ejection direction. This tangentialvelocity is approximately a third of the ejection velocity. Since thepoint of extraction and the direction of ejection are known for everyzone an ejection guide can be added to the cradle to prevent fired casesfrom striking the weapon or crew. Since the ejection mechanism ispositive (that is, no springs or pressure systems are employed) the caseis certain to be ejected even if high breech sealing forces exist.

We claim:

1. An automatic. rapid firing. artillery piece. comprising:

support means having a first longitudinal axis;

a single tube. having a second longitudinal axis parallel to said firstlongitudinal axis, and mounted to said support means for reciprocationalong said second longitudinal axis in recoil and counterrecoil;

a breech assembly. having a plurality of chambers disposed in an annularrow about a third longitudinal axis which is parallel to said firstlongitudinal axis. and mounted to said support means aft of said tubefor reciprocation along said third longitudinal axis in recoil andcounterrecoil and for rotation about said third longitudinal axiswhereby to sequentially align each of said plurality of chambers withthe aft end of said tube on said first longitudinal axis; and

loading means. mounted to said support means. including transport meansfor transporting a round of ammunition in either of two oppositedirections along a path parallel to said third longitudinal axis from aninitial, fixed station. sensing means coupled to said breech assemblyfor providing a signal responsive to the recoil velocity of said breechassembly. first actuating means coupled to said transport means and saidsensing means for moving said transport means in an appropriate one ofsaid two opposite directions and at an appropriate variable velocity toa variable station along said path which will be functionally adjacentthe aft end of one of said chambers at the nadir of recoil travel ofsaid breech assembly. whereby the round will be chambered in said onechamber at low relative velocity between said transport means and saidbreech assembly 2. An artillery piece according to claim 1 wherein saidbreech assembly includes:

a breech containing said plurality of chamber; and

second actuating means operable during counterrecoil travel of saidbreech for indexing said breech about said third longitudinal axis toshift the next chamber in sequence into alignment with said tubev 3. Anartillery piece according to claim 1 wherein said breech assemblyincludes:

a breech containing said plurality of chambers which are two in numberand disposed diametrically about said third longitudinal axis;

extraction means. operable during the recoil travel of said breech, forextracting the case of the last fired round from the last fired chamber;and

second actuating means. operable during counterrecoil travel, forrotating said breech for shifting said last fired chamber out ofalignment with said tube and the loaded chamber into alignment with saidtube.

4. An artillery piece according to claim 3 wherein said support meansincludes:

a cradle having a plurality of ways extending parallel to said firstlongitudinal axis;

fore and aft plates and a main center rod fixed therebetween parallel tosaid first longitudinal axis:

said breech assembly includes a breech support assembly having runnersmating with said cradle ways; and

fore and aft plates capturing said breech therebetween. said breech andfore and aft plates having respective longitudinal bores therethroughand passing said main center rod therethrough. whereby said breech isadapted to rotate about said main center rod.

5. An artillery piece according to claim 4 wherein:

said second actuating means includes a cylindrical cam means having acentral longitudinal bore receiving said main center rod therethroughand an exterior surface having two cycloidal cam slots and twolongitudinal return cam slots diametrically spaced apart therein withforward and rearward intersections respectively. said cylindrical carnmeans being keyed to said main center rod and free for relativelongitudinal movement only, and having additional interlock meansadapted to preclude forward longitudinal movement of said cylindricalcam means relative to said main center rod;

said breech being joumaled on said cylindrical cam means and having twodiametrically spaced apart cam slot followers respectively engaging saidcam slots in said cylindrical cam means and adapted to follow saidlongitudinal return cam slots during rearward movement relative to saidcylindrical cam means and to follow said cycloidal cam slots duringforward movement relative to said cylindrical cam means;

whereby. immediately prior to the firing of a round of ammunition. saidbreech and said cylindrical cam means are in their respectiveforwardmost positions with said cam followers in said forwardintersections of the cycloidal and return slots; and

subsequent to firing. said breech recoils rearwardly with said camfollowers riding in said return slots. and said cam means stationary.until said cam followers reach said rearward intersections of thecycloidal and return slots. causing said cam means to travel rearwardlywith said breech until said breech reaches its nadir of recoil travel.and said additional interlock means becomes operable to preclude forwardmovement of said cam means; whereupon said breech counterrecoilsforwardly with said cam followers riding in said cycloidal slots causingsaid breech to rotate with to respect to said stationary cam means untilsaid cam followers reach said forward intersections of the cycloidal andreturn slots and deoperate said additional interlock 'means to permitforward movement of said cam means and causing said cam means to travelforwardly until said breech reaches its battery positron.

6. An artillery piece according to claim 5 wherein:

said additional interlock means comprises two diametrically spaced apartlongitudinal series of rearwardly pointed teeth cut into said maincenter rod. and

two forwardly pivoted latching dogs respectively disposed in saidforward intersections of said cam slots and extending centrifugally tonormally engage with said respective series of teeth and adapted to beactuated. by said rollers when they are in said forward intersections.to disengage from said teeth.

7. An artillery piece according to claim I wherein:

said transport means includes a tray for receiving and sup porting around of ammunition;

said first actuating means including a ram having a longitudinallyextending rack;

a cylinder fixed to said breech and having a longitudinally extendingrack;

a piston, disposed in said cylinder. having a longitudinally extendingmember fixed to a gear housing. and having a longitudinal orificethrough said piston between the forward and aft sides thereof;

two gears fixed to a common shaft in said gear housing. one gear meshedwith said rack of said ram. the other gear meshed with said rack of saidcylinder;

said sensing means includes spring means normally biasing said gearhousing and piston forwardly in the counterrecoil direction;

hydraulic fluid disposed in said cylinder and adapted to flow betweensaid forward and aft sides of said piston through said orifice; and

whereby the direction and velocity of movement of said ram is responsiveto the combined effects of the direction and which is responsive to theflow rate of through said position orifice.

said hydraulic fluid

